Rubber stabilized against ozone deterioration by use of morpholine additives

ABSTRACT

SULFUR-CURED SBR IS STABILIZED AGAINST OZONE DETERIORATION BY THE ADDITION OF N-(P-ISOPROPYLAMINOPHENYL) MORPHOLINE, N-(P-CYCLOHEXYLAMINOPHENYL) MORPHOLINE, N-(PISOPROPYLAMINOPHENYL) 2,6-DIMETHYL MORPHOLINE OR N-(PCYCLOHEXYLAMINOPHENYL) 2,6-DIMETHYL MORPHOLINE.

United States Patent T 3,557,054 RUBBER STABILIZED AGAINST OZONE DETERI- ORATION BY USE OF MORPHOLINE ADDITIVES Richard W. Kibler, Cuyahoga Falls, Ohio, assignor to The Firestone Tire & Rubber Company, Akron, Ohio, a corporation of Ohio N0 Drawing. Filed July 21, 1965, Ser. No. 473,821 Int. Cl. C08c 11/00; C08d 7/10 US. Cl. 26045.8 6 Claims ABSTRACT OF THE DISCLOSURE Sulfur-cured SBR is stabilized against ozone deterioration by the addition of N-(p-isopropylaminophenyl) morpholine, N-(p-cyclohexylaminophenyl) morpholine, N-(pisopropylaminophenyl) 2,6-dimethyl morpholine or N-(pcyclohexylaminophenyl) 2,6-dimethyl morpholine.

This invention relates to new antiozonants and antioxidants (referred to herein as antiozonants) for use in natural and synthetic rubber vulcanizates, their prepara tion, rubbers containing them, and the method of curing rubbers in the presence of the new compounds.

The new compounds have the following formula in which (a) when X is O, R is hydrogen or an alkyl group of 1 to carbon atoms, and R and R are selected from the class consisting of straight and branched chain and hydroxy alkyl groups of 1 to carbon atoms and aryl groups (e.g., phenyl, naphthyl, alkylphenyl, alkoxyphenyl, etc., in which the alkyl group is a lower branched or straight chain alkyl group of 1 to 4 carbon atoms); except that R CHR may be a cycloalkyl group of 5 to 8 carbon atoms; and

(b) when X is NH or R is hydrogen, and R and R is each selected from the class consisting of straight and branched chain alkyl groups of 1 to 10 carbon atoms and aryl groups (e.g. phenyl, naphthyl, alkylphenyl, alkoxyphenyl, etc., in which the alkyl group is a lower straight or branched chain group of 1 to 4 carbon atoms), except that R CHR may be a cycloalkyl group of 5 to 8 carbon atoms.

Representative compounds are:

3,557,054 Patented Jan. 19, 1971 N,N-bis (p-isopropylaminophenyl) piperazine N- [p-2 (4-hydroxy-4-methylpentyl aminophenyl] morpholine N p-2 (4-hydroxy-4-methylpentyl) aminophenyl] -2,6-dimethyl morpholine N- p-2 5 -hydroxyhexyl) aminophenyl] -2,6-dimethyl morpholine The rubbers which may be improved by the antiozonants are diene rubbers, i.e., natural and synthetic homopolymers and synthetic copolymers of hydrocarbon dienes containing 4 and 5 carbon atoms (viz. butadiene, isoprene and piperylene), the copolymers being copolymers of such dienes with monomers such as styrene, alkyl-substituted styrenes, vinyl toluenes, acrylonitrile, lower-alkyl acrylate and methacrylate esters, etc.

The antiozonants are readily prepared from N(4-nitrophenyl) morpholine, or an identically substituted 2,6-disubstituted morpholine (the substituents being alkyl groups of 1 to 8 carbon atoms), or N(4-nitrophenyl) piperazine or N,N'-bis-(4-nitrophenyl) piperazine. The nitro compound is reacted with a ketone and hydrogen which on reduction reaction with the nitro group (usually with a catalyst) gives the desired aminophenyl grouping. The ketone has the formula O:CR R in which R and R have the values given in the foregoing formula for the antiozonant. These ketones include:

acetone cyclohexanone 2-octanone 2-butanone 4-methyl-2-butanone propiophenone benzophenone dibenzylketone phenylacetone acetophenone cyclohexyl phenyl ketone and ketones in which there are homologous alkyl groups of 1 to 10 carbon atoms.

The following examples illustrate the preparation of such compounds, and the preparation of N(4-nitrophenyl) morpholine and N(4-nitrophenyl) 2,6-dimethyl morpholine is included.

PREPARATION OF N-(4-NITROPHENYL) MORPHOLINE In a 1-liter round-bottom flask fitted with a reflux condenser, a thermometer and a mechanical stirrer was placed 158 gr. (1 mole) of 1-chloro-4-nitrobenzene and 264 ml. (ca. 3 moles) of morpholine. The reactants were heated at reflux with stirring ofr about 4 hours and then allowed to cool. The reaction mixture was slurried with water and filtered. The yellow crystalline solid was washed with water and air dried. The product melted at -151 C.

EXAMPLE 1 Preparation of N-(p-isopropylaminophenyl) morpholine 3 EXAMPLE 2 Preparation of N-(p-2-octylaminophenyl) morpholine The title compound was prepared in the same manner as in Example 1 except that 2-octanone was used in place of the acetone. The product was a colorless solid melting at 6061 C.

Analysis.Calcd for C H N O (percent): C, 74.74; H, 10.20; N, 9.40. Found (percent): C, 74.45; H, 10.42; N, 9.65.

EXAMPLE 3 Preparation of N-(p-cyclohexylaminophenyl) morpholine This compound was prepared in the same manner as shown in Example 1 except that cyclohexanone was used in place of acetone. The product was worked up and purified in the usual manner and melted at 126127 C.

Analysis.Calcd for C H N O (percent): C, 73.80; H, 9.29; N, 10.76. Found (percent): C, 73.65; H, 9.39; N, 11.07.

EXAMPLE 4 Preparation of N-(p-sec-butylaminophenyl) morpholine This compound was prepared in the same manner as shown in Example 1 except that Z-butanone was used in place of the acetone. The colorless crystalline product melted at 8587 C.

Analysis.-Calcd for C H N O (percent): C, 71.76; H, 9.46; N, 11.98. Found (percent): C, 71.70; H, 9.36;

EXAMPLE 5 Preparation of N-[p-2-(4-methylphenyl)aminophenyl] morpholine This compound was prepared in the same manner as shown in Example 1 except that 4-methyl-2-pentanone was used in place of the acetone. The product was isolated in the usual manner and melted at 6466 C.

Analysis.Ca1cd for C H N O (percent): C, 73.23; H, 9.99; N, 10.68. Found (percent): C, 73.05; H, 10.10; N, 10.68.

Preparation of N-(p-nitrophenyl)-2,6-dimethyl morpholine In a 1-liter round-bottom flask fitted with a reflux condenser, a mechanical stirrer and a thermometer was placed 158 gr. (1.0 mole) of 1-chloro-4-nitrobenzene and 351.0 gr. (3.0 moles) of 2,6-dimethyl morpholine. The reaction mixture was heated at reflux with stirring for four hours, cooled and filtered. The orange crystalline product was air dried.

EXAMPLE 6 Preparation of N-(p-isopropylaminophenyl)-2,6-dimethyl morpholine The N-(p-nitrophenyl)-2,6-dimethyl morpholine (11.8 gr., 0.05 mole), acetone (3.2 gr., 0.055 mole), glacial acetic acid (1 ml.), platinum oxide (0.2 gr.), and absolute ethanol (100 ml.) were mixed and hydrogenated on a Paar Hydrogenator Apparatus at an initial hydrogen pressure of 50 p.s.i.g. When the uptake of hydrogen had ceased, the reaction mixture was filtered to remove the catalyst and evaporated leaving an oily residue which was purified by chromatography on alumina. The product was a red viscous oil.

Analysis.--Calcd for C H N O (percent): C, 72.53; H, 9.74; N, 11.28. Found (percent): C, 71.40; H, 9.71; N, 10.97.

EXAMPLE 7 Preparation of N-(p-cyclohexylaminophenyl)-2,6- dimethyl morpholine This compound was prepared in the same manner as in Example 6 except cyclohexanone was used in place of the acetone. The oil product was purified by chromatography on alumina.

4 Analysis.-Calcd for C H N O (percent): C, 74.95; H, 9.78; N, 9.73. Found (percent): C, 74.92; H, 9.83; N, 9.61.

EXAMPLE 8 Preparation of N-(p-cyclohexylaminophenyl) piperazine A mixture of N-(p-nitrophenyl) piperazine (10.3 gr., 0.05 mole), cyclohexanone (5.4 gr., 0.055 mole), glacial acetic acid (1 ml.), platinum oxide (0.1 gr.) and absolute ethanol (100 ml.) was hydrogenated at an initial hydrogen pressure of 50 p.s.i.g. After the uptake of hydrogen had ceased, the reaction mixture was filtered and evaporated. The residue was dissolved in ether (only partially soluble) and filtered. The ether soluble material was chromatographed on alumina. The ether eluates upon recrystallization from ether melted at 101102 C.

Analysis.-Calcd for C H N (percent): N, 16.20. Found (percent): N, 15.90.

The antiozonants are added to the rubber in any usual antiozonant amount together with sulfur and other compounding ingredients and cured at a usual temperature.

MORPHOLINE ANTIOZONANT CURES The following table gives the physical properties of test samples containing 2 parts of different antiozonants in butadiene-styrene copolymer (GR=S) in a usual sulfurcontaining formula, the rubbers having been cured for 60 minutes and 280 F., and then subjected to aging 2 days in an oven at 212 F., and antiozonant evaluation in a dynamic test on samples exposed to an atmosphere containing 60 parts per million of ozone for 7 hours at F. The ozone cracking was graded on this scale: very, very slight (v.v.sl.) and slight ($1.), with a plus or minus to indicate greater or less cracking, respectively, than indicated by the abbreviation. The test materials are identified as A=N(p-isopropylaminophenyl) morpholine B=N(p-sec-butylaminophenyl) morpholine C=N(p-2-octylaminophenyl) morpholine D=N(p-cyclohexylaminophenyl) morpholine E=N(p-isopropylaminophenyl)-2,6-dimethy1 morpholine F=N(p-cyclohexylaminophenyl)-2,6-dimethy1 morpholine [Physical properties] Test material A B C D E F Before Aging:

300% modulus, p.s.i 1, 475 1, 475 1, 500 1, 325 1, 600 1, 500 400% modu1us, p.s.i 2, 200 2, 200 2, 400 2, 2, 275 2, 300 Tensile strength, p.s.1 3, 350 3, 200 3, 700 3, 400 3, 300 3, 375 Elongation, percent 580 520 580 550 560 560 After Aging:

300% modulus, p.s.i, 2, 800 2, 525 2,700 2, 300 2, 900 2, 400 Tensile strength, p.s.i 2, 800 2, 525 3, 225 2, 775 2, 900 2, 825 Elongation, percent-.. 300 300 320 350 300 300 Ozone cracking 1 Very, very sligl1t+. 2 Sligl1t+.

Toxicity tests on all of these compounds showed them to be devoid of any adverse toxic effect.

What I claim is:

1. The composition of a sulfur-cured, butadiene-styrene rubber which contains an antiozonant amount of a compound of the class consisting of N-(p-isopropylaminm phenyl) morpholine, N-(p-cyclohexylaminophenyl) morpholine, N-(isopropylaminophenyl) 2,6-dimethyl morpholine, and N-(p-cyclohexylaminophenyl) 2,6-dimethyl morpholine.

2. The composition of claim 1 in which the compound is N-(p-isopropylaminophenyl) morpholine.

3. The composition of claim 1 in which the compound is N- (p-cyclohexyla'minophenyl) morpholine.

4. The composition of claim 1 in which the compound is N-(isopropylaminophenyl) 2,6-dimethyl morpholine.

5. The composition of claim 1 in which the compound is N-(p-cyclohexylaminophenyl) 2,6-dimethyl morpholine.

6. The composition of a sulfur-cured, butadiene-styrene rubber which contains an antiozonant amount of a compound selected from the group consisting of N-(p-isopro- 6 References Cited UNITED STATES PATENTS 1,899,058 2/1933 Reed 260 800 3,163,616 12/1964 St'aley 26()8'00X DONALD E. CZAJA, Primary Examiner M. J. WELSH, Assistant Examiner US. Cl. X.R.

pylaminophenyl) morpholine and N-(p-cyclohexylamino- 10 260 247 5, 268, 800

phenyl) morpholine.

55 5 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,O5' l- Dated January 19, 1971 Richard W. Kibler Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

' Col. 2, line 52, "ofr" should read --for-- lines 61 and 62 should read as follows:

"m01e) acetone: (6. gr. 0.11 mole) glacial ace acid (1 ml.) platinum oxide (0.1 gr.) and line 70, H H O" should read --C13H2ON2O-- Signed and sealed this 29th day of June 1971.

(SEAL) Attest:

'1 T I X I J R @WARD M.FL1:.TC1-MR JR. NILLIAM E. SCHUYLBJR, Attesting Officer Commiss oner of Patents 

